High octane motor fuel production by alkylation and reforming



United States Patent HIGH 8 Claims ABSTRACT OF THE DISCLOSURE Highoctane number motor fuel is produced by alkylating isobutane with a Cmono-olefin to produce an alkylate separable into distinct low octaneand high octane fractions, reforming the low octane fraction andblending it with the high octane number alkylate fraction.

CROSS-REFERENCE TO RELATED APPLICATION This application is acontinuation-in-part of my copending application Ser. No. 668,684, filedSept. 18, 1967, now abandoned.

FIELD OF INVENTION This invention pertains to the production of highoctane number motor fuel involving a combination of alkylation andreforming. In particular, this invention pertains to the alkylation ofisobutane with a C. mono-olefin to form an alkylate readily separableinto a high octane number and a low octane number alkylate fraction, thereforming of the low octane number fraction and the blending of theresultant reformate with the high octane number alkylate fraction.

DESCRIPTION OF PRIOR ART Production of C -C1 branched paraflins havinghigh octane numbers and anti-knock properties suitable for use inautomotive and aviation fuels is of considerable importance to therefinery industry. This is a result of the introduction ofhigh-compression, high-performance automobile engines and the necessityfor high octane motor fuels required to develop maximum power therefrom.As automotive engine manufacturers develop engines with increasedperformance characteristics, higher octane motor fuels are required andslight variances in octane numbers become a critical parameter in anengines performance. For example, an octane rating increase in a motorfuel of as little as 2-3 numbers can be the difference between a quietor a knocking engine. In

addition, the demand for clear, unpolluted air has placed an emphasis ondeveloping a motor fuel having superior anti-knock properties withoutthe need for anti-knock additives such as tetraethyllead which pollutethe air when expelled with the engine exhaust.

A common source of high octane number motor fuels .is the catalyticalkylation of low boiling isoparaflins, such as isobutane andisopentane, with mono-olefins such as propylene, the butylenes, theamylenes and mixtures thereof. The common commercial processes utilizedtoday involve the alkylation of isobutane with butylenes and/ or.propylene. These processes typically produce a motor fuel alkylatehaving a research clear octane rating of 93-95.

It is well recognized in the prior art that the components present in atypical motor fuel alkylate process constitute a diverse mixture of bothhigh octane and low octane C C isomers. The prior art further recognizesthat the only portion of the alkylate product having a ice low octanenumber, readily separated from the total alkylate product, is the highboiling portion of the alkylate commonly referred to as alkylatebottoms. As is Well known to those trained in the art, a typicalalkylate, produced by the catalytic alkylation of isobutane and/orisopentane with propylene, butylenes and amylenes, has a 50% volumetricdistillation temperature of about 200- 240 F. and a temperature of about300350 F. and often extending up to 400 F. The initial boiling pointvaries by the amount of butane etc., present, a determined by theparticular use of the fuel and season of the year in which it isproduced. The art recognizes that the very high boiling portion of thealkylate mentioned above is of a lower octane number than the rest ofthe alkylate produced, namely, that portion of the alkylate boiling over270-400 F. For example, Leifer, in U.S. Patent No. 2,401,649, alkylatesisobutane and butylenes in a conventional alkylation zone to produce analkymer gasoline rich in isooctane. This is obtained by separating fromthe alkylate product a fraction having an end boiling point of about 350F. and an octane number of about 92. Higher boiling constituents areremoved and passed to a reforming zone for conversion to lower boiling,higher octane constituents. Deanesly, in US. Patent No. 2,684,325,separates a polymerizationalkylation reactor efiiuent to recover afraction boiling up to 400 P. which is utilized as a goline blendingcomponent. The distillation residue boiling over 400 F., andrepresenting about 10% by volume of the alkylation product, is recycledfor upgrading to lower boiling stocks. Findlay, in US. Patent No.2,80,995, separates a light deolefinized gasoline fraction having an endboiling point (EBP) of about F., and an octane number of about 60.4 froma conventional HF isobutane alkylation unit, reforms this light fractionand blends the resultant reformate with the higher boiling alkylateproduct to produce an upgraded gasoline product. Chapman, in US. PatentNo. 3,211,808, separates a heavy alkylate, produced in a conventional HFalkylation unit and defined as having an initial boiling point (IBP) of260 F. from the total alkylate product and recycles this fraction to thealkylation unit to produce a higher octane number motor fuel.

Thus, it is readily seen that the prior art recognizes that a smallportion of either the light alkylate (EBP of about 200 F.) and, moreparticularly, a portion of the heavier alkylate (IBP of about 260-400F.) are undesirable constituents in a motor fuel alkylate since theypossess lower octane numbers than the rest of the motor fuel alkylate.

SUMMARY OF THE INVENTION It has now been discovered that a typicalalkylate produced by isobutane-butylene alkylation is readily separableinto not only two-i.e., heavy alkylate and light alkylate-fractionshaving distinct octane number differences, but into three suchfractions. It has been discovered, that in addition to the recognizedlow-octane heavy alkylate fraction, there exists an alkylate fractionhaving an initial boiling point of about 200 F. to about 230 F. whichhas an octane number of about 10 octane numbers below the IBP to 200230F. fraction without inclusion of the traditional heavy alkylatefraction. Inclusion of the heavy alkylate fraction increases the octanenumber difference to even a greater degree. This lower octane fractionis characterized in havinga substantially higher dimethylhexane contentthan the higher octane fraction. This fraction possesses this loweroctane rating despite the presence of appreciable amounts of high octanetrivmethylpentanes. This result is due to the nonlinearity 1 3 I hexanecontent means that the dimethylhexane content of the lower octane numberfraction is at least twice the content present in the higher octanenumber fraction.

Accordingly, it is an object of this invention to provide a process forproducing high octane number motor fuel. It is a further object toproduce such fuels by a unique combination of alkydation, separation andreforming.

In an embodiment, this invention relates to a process for producing highoctane number motor fuel which comprises the steps of: (a) alkylatingisobutane with a C mono-olefin in contact with an aikylation catalyst atalkylation" conditions in an alkylation zone to produce an alkylateproduct cotaining dimethylhexanes; (b) separating said alkylate into alow-boiling, high-octane fraction and a high-boiling, low-octanefraction characterized by a dimethylhexane' content substantially higherthan said low-boiling fraction and having an initial boiling point ofabout 200 F. to about 230 R; (c) reforming at least a portion of saidlowerEbctane, high-boiling fraction, in admixture with hydrogen and incontact with a reforming catalyst at reforming conditions in a reformingzone to produce a higher octane reformate; (d) commingling at least aportion of said higher octane reformate with said high-octane,low-boiling alkylate fraction to produce a motor fuel alkylatepossessing a higher octane: number thansaid alkylate product producedinstep (a).

In a further more limited embodiment, the aforemen tioned high-boiling,low-octane number fraction consists of about 301 to about 60 volumepercent of said alkylate product.

Alternative embodiments and a more detailed description of thealkylation and reforming zones hereinbefore mentioned will be found inthe following description of the preferred embodiments:

" DESCRIPTION on THE rREEERaED EMBODIMENTS The alkylation step of theprocess of this invention preferably comprises alkylating isobutane anda butylene, inasmuch as the ideal alkylation product of these species isa branched C parafiin. However, it is within the scope of thisginventionto include, in addition to isobutane and butylenes, a mixed hydrocarbonfeed stock containing olefinic hydrocarbons such as propylene, amylenes,etc., as Well as C to C parafiins. If such mixed streams are utilized,it ispreferred that the C mono-olefins (butylcues) and isobutanepredominate in the hydrocarbon mixture. P

The alkylation step of the process of this invention comprisescontacting a hydrocarbon feed stock containing isobutane and butyleneswith an acid-acting alkylation catalyst in an alkylation zone. Theisobutane and butylene may be introduced as separate feed streams or inadmixture with one another. This contacting is preferably efiected byintimately mixing the hydrocarbons with a strong acid catalyst such ashydrofluoric acid, sulfuric acid, mixtures of sulfuric iand phosphoricacids, certain complexes of aluminum chloride and sulfuric acid, etc.Preferred alkylation catal jsts are hydrofluoric acid and sulfuric*acid, particularly hydrofluoric acid. It is also within the scope ofthis invention to effect the alkylation by contacting the hydrocarbonwith a suitable solid alkylation catalyst.

To prevent polymerization of the olefin in the alkylation zone, thecatalyst and hydrocarbons; are maintained in intimate physical admixture'and a large mole excess of isobutane to olefin is used. Thisisobutane-olefin mole ratio can vary from about 2:110 about'20zl andpreferably from about 6:1 to about 16:1. This excess isobutane isreadily separated from the resultant alkylation product and is usuallyrecycled to the alkylation zone. When a liquid acid such as hydrofluoricor sulfuric acidis utilized to catalyze the alkylation reaction, acatalyst to hydrocarbon volume ratio of about 0.25:1 to about 10:1 andparticularly about 0.5:1 to about 5.0:1 are employed. The

reaction is effected at a temperature of about 0 F. to, 200' F., aresidence time of about 20 seconds to about 1200 seconds, and preferablyabout 60 to about 1000 sec; onds, and a pressure of about atmospheric toabout 50 atmospheres. It is particularly preferred to maintain areaction pressure sufiicient to maintain the catalyst and reactants inthe liquid phase. After the termination of the desired residence time,the resulting alkylation zone efiluent is separated into a hydrocarbon,phase and an acid phase. From the hydrocarbon phase, isobutane and otherlight hydrocarbons such as butane are recovered, leasing a desiredamount of butane within the alkylate to control the vapor pressure ofthe alkylate. As used herein, alkylateirefers to the higher molecularweight reaction product from the alkylation reaction. The high molecularweight tars, etc., formed Within the reaction are also removed byappropriate distillation techniques. The resultant alkylate is thenseparated into a high-octane, lowboiling fraction characterized inhaving an EBP of about 200 F. to about 230 F. and a lower-octane, highboiling fraction, characterized in having an IBP of aboutr200 F. toabout 230 F. This lower octane fraction is further characterizedin thatthe dimethylhexanes formed by the isobutane-butylene alkylation reactionare predominantly in this fraction; namely, the :dimethylhexane contentof this fraction is at least twice that of the higher octane fraction.This lower octane fraction typically consists of about 30 to about 6;)volume percent of the total alkylate product. This exact value is afunction of the amount of propylene in the alkylation zone feed stockand the C isoparafiins produced as a result. This foregoing separationis readily obtained by conventional fractional distillation techniques.i 7 I At least a portion of the high-boiling, lower-octane fraction isthen passed to a reforming zone wherein the lower octane constituents inthis fraction are converted to higher octane components byg the variousreactions which occur in a reforming zone such as isomerization,dehydrocyclization, and cracking. As used herein, the term at least aportion refers to eithera homogenous portion of said fraction or anappropriate boiling fraction of this fraction. It is particularlypreferred to operate this reforming zone in the presence of addedhydrogen so that this resultant reformate will be essentiallyolefin-free. While the dehydrogenation of paraflins to olefins canproduce a higher octane product, the olefins are an un: desiredconstituent in a motor fuel product because of their tendency to formgum deposits when utilized in internal combustion engines.

The conditions, catalystaand methods of reforming paraflinichydrocarbons are well known to the art. No patentable novelty is claimedherein for the method of alkylating isobutane and butylenes and thereforming of the herein described lower octane number alkylate fraction.The inventive concept resides in the advantageous, heretoforeunrecognized, method of combining these two well known refiningprocesses to produce a high octane motor fuel as hereinbefore described.

Suitable reforming catalysts typically include the dualfunctioncatalysts typified in having a heavy metal component to induce ahydrogenanon-dehydrogenation function to an acid-acting crackingmaterial of the porous, adsorptive, refractory .oxide type. While theknown chromia-alumina type catalysts are applicable, it is pre ferred toutilize a reforming catalyst comprising a Group VIII metallic-Lcomponent, a halogen component, and suitable refractory inorganic oxidessuch as the high surface area gamma-, eta-, and theta-aluminas.Particularly preferred are the gamma-aluminas. By the term high surfcearea is meant a surface area as measured by conventional surfaceadsorption techniques, of about 25 to about 500 or more square metersper gram, and preferably a surface area of approximately to 300 squaremeters per gram. In addition to the aforementioned aluminas, it is alsocontemplated that other refractory inorganic oxides containing at leastone metal from Group VIII of the Periodic Table, such as silica,zirconia, mag nesia, thoria, etc., and combinations of the variousrefractory inorganic oxides containing at least one metal from GroupVIII of the Periodic Table such as silica alumina, alumina-magnesia,alumina-thoria, aluminazirconia, 'etc., may also be utilized ascatalysts in the reforming zone of the present invention. In addition,crystalline aluminosilicates, both synthetic and natural occurring, mayalso be utilized as solid supports for the reforming catalyst. It ispreferable that the pore mouths of the crystalline aluminosilicates havecross-sectional diameters of from about 4 to 15 angstrom units. Amongthe preferred crystalline aluminosilicates are the hydrogen and/orpolyvalent forms of faujasite and mordenite and particularly thehydrogen form of mordenite. The concentration of crystallinealuminosilicate may be as high as 100%, or the crystallinealuminosilicate may be held within a matrix such as silica, alumina andsilica-alumina.

Typical metals from Group VIII of the Periodic Table for use in thereforming catalyst to be utilized in the reforming zone of the presentinvention include platinum, palladium, ruthenium, rhodium, osmium, andiridium, and mixtures thereof. Platinum and palladium are particularlypreferred. In addition, the Group VIII metal may also be present withmetals, such as rhenium, known p EXAMPLE The following example ispresented 'to further illustrate the embodiments of the process of thisinvention and is not intended to be an undue limitation on the broadscope and spirit of the appended claims.

An olefin mixture containing propylene, butylenes, and amylenes, themajority of which are butylenes, was alkylated with isobutane in aconventional commercial alkylation system utilizing hydrogen fluoride asa catalyst. This system was maintained at alkylation conditionsincluding a 12:1 isobutane to olefin mole ratio, an operatingtemperature of about 85 F., a residence time of about 420 seconds, ahydrogen fluoride to hydrocarbon volume ratio of about 1.5 :1 and anoperating pressure of about 175 p.s.i.g. After separation of the excessisobutane, catalyst, and tars produced during the course of thereaction, a motor fuel alkylate having a 94.2 research clear octanenumber was recovered.

This sample was then subjected to an intensive analysis including octanenumber evaluation and component analysis. The sample was divided intoten equal volume portions by fractional distillation and each portionwas analyzed to determine its composition and research octane number.This complete evaluation is presented in the following table.

OCTANE NUMBER EVALUATION AND COMPONENT ANALYSIS OF ALKYLATE ResearchFraction No.

Octane No. 1 2 3 4 5 6 7 8 9 Botts.

Cut temp. F 164. 3 206. 6 211. 1 215. 6 219. 2 236. 3 240. 0 293 293+Volume percent 10 10 10 10 10 10 10 10 10 Alkylate component (type)weight percent: i-Butane 102. 5

n-Butane 95.0 2 2 0.1 i-Pentane 92. 3 1. 6 0. 1 n-Pentane 61. 7 1. 5

5 a 2,3-dimethylbutane. 103. 5 28. 8 0. 7 2-methylpentane 73. 4 13. 6 0.3 3methylpentane 74. 5 4. 2 0. 2 n-Hexane 24. 8 0.2 2,2-dimethylpenta92. 8 0. 1 2,4-d1methylpentane 83. 1 19.8 17. 6 2,2,3-trirnethylpentane.112. 1 1. 3 O. 4 2-methylhexane 42. 4 1. 6 1. 7 2,3-dimethy1pentane...91. 0 22. 8 24. 5 3-methylhexane 52. 0 1.2 1.1 2,2,4-trimethylpentane100 1. 1 3 56. 9 18. 7 2. 2,5-dimethylhexane 55. 5 14.0 14. 9 7. 82,4-dime thylhexane 65. 2 16. 7 18. 4 10. 6 2,2,3-tri methylpentane 109.6 2. 2 2.8 2. 2 2,3,4-trimethylpentane 102.7 6. 2 25. 5 31. 3 2,2,3trimethylpentane 106. 1 1. 8 13. 9 27. 9 2,3-dimethylhexane 71. 0 1. 15. 8 14. 6 0 70-75 2. 7

0t 100. 0 100. 0 100. 0 Research clear octane No., 10% fraction 88.9 87.1 90. 5

to be capable of stabilizing a reforming catalyst. The Group VIIIcomponent of the catalyst will normally be utilized in an amount of fromabout 0.1% to about 2.0% by weight and the amount of combined halogen inthe reforming catalyst can vary from about 0.01 to about 2.0% by weightbased upon the solid support. Of the various halogens which may beutilized, both fluorine and chlorine, particularly chlorine, arepreferred.

Within the reforming zone, the low octane number alkylate fraction, inadmixture with hydrogen is contacted with the foregoing catalystpreferably maintained in a fixed bed. This reforming zone is maintainedat re forming conditions which include a temperature of about 700 toabout 1100 F., a pressure of about 0 to about 1,000 p.s.i.g., an LHSV(liquid hourly space velocity) of about 0.1 to about 10 hr. and a moleratio of hydrogen to hydrocarbon of about 1:1 to about 20:1 or more.

The resulting reactor effluent is then recovered and after separation ofhydrogen and light hydrocarbons is blended by meanswell known to the artwith the low-boiling, high-octane alkylate fraction to produce a highoctane motor fuel typically having a research octane in excess of 95.

An examination of the data presented in the foregoing table yields somerather unexpected, unanticipated results. It is readily seen that thealkylate, in addition to the lower octane alkylate bottoms (i.e.,260-300+) fraction known to the art as having a lower octane number thanthe rest of the alkylate, there exists a sharp difference in the octanenumbers obtained for the first five 10% cuts than for the last five 10%cuts. This sharp unexpected difference of about 10 octane numbersbetween these segments appears to be the result of the presence of lowoctane number dimethylhexanes within each fraction. The presence ofthese compounds, despite the presence of appreciable amounts of highoctane number trimethylpentanes in these cuts, yields a marked octanedifference in comparison to the first five 10% cuts where thesedimethylhexanes are not present. This difference is observed in otheralkylates produced within both commercial and laboratory research units.

This foregoing alkylate is then fractionated to produce a high-octane,low-boiling fraction which represents 50% of the total alkylate and hasan IBP -2l6 F. boiling range. The remaining alkylate (216 F.+), having alower octane number, is then reformed in admixture with hydrogen in aconventional reforming zone containing a reforming catalyst comprisingalumina combined with 0.6 wt. percent platinum and 0.8 wt. percentchloride. This reforming zone is maintained at a temperature of about850-F., a pressure of 500 p.s.i.g., a liquid hourly space velocity of1.0 hrr and a hydrogen tohydrocar'bon mole ratio of 10.0:1.0. Withinthis reforming zone portions of this alkylate are cracked,dehydrocyclized, and/or isomerized to produce a higher octane reformate.This reformate is then blended with the low-boiling, high-octanefraction to yield a final motor fuel having a research octane number of98.5. This is a considerably higher octane number than that obtained byalkylation alone.

Thus, it has been shown that there exists a heretofore unrecognizedspecific fraction in an alkylate produced by isobutane-butylenealkylation which, in addition to the recognized heavy alkylate fraction,has an octane number significantly below that of the remaining alkylate.By removing and reforming this fraction, 21 motor fuel having animproved octane number is available by methods heretofore unrecognizedin the art.

I claim as my invention:

1. A process for producing high octane number motor fuel which comprisesthe steps of (a) alkylating isobutane with a C mono-olefin in contactwith an alkylation catalyst at alkylation conditions in an alkylationzone to produce an alkylate product containing dimethylhexanes;

('b) separating said alkylate into a low-boiling, highoctane fractionand a high-boiling, low-octane fraction characterized by adimethylhexane content substantially higher than said low boilingfraction and having an initial boiling point of about 200 F. to about230 F.;

(c) reforming at least a portion of said lower octane high-boilingfraction, in admixture with hydrogen and in contact with a reformingcatalyst at reforming conditions in a reforming zone to produce a higheroctane reformate; and,

(d) commingling at least a portion of said higher octane reformate withsaid high-octane, low-boiling alkylate fraction to produce a motor fuelalkylate possessing a higher octane number than said alkylate productproduced in step (a).

2. The process of claim 1 further characterized in that said alkylationconditions include a temperature of about 0 F. to about 200 F., acontact time of about 20 seconds to about 1200 seconds, a catalyst tohydrocarbon volume ratio of about 0.5 :1 to about 5:1, a isobutane toolefin mole ratio of about 2:1 to about 20:1, and a pressure of aboutatmospheric to about atmospheres.

3. The process of claim 1 further characterized in that said alkylationcatalyst is hydrogen fluoride.

4. The process of claim 1 further characterized in that said alkylationcatalyst is sulfuric acid.

5. The process of claim 1 further characterized in that said reformingcatalyst comprises a platinum component and a halogen component with arefractory inorganic oxide carrier material, and said reformingconditions include a temperature of about 700 F. to about 1100 F., apressure of about 0 to about 1000 p.s.i.g., a liquid hourly spacevelocity of about 0.1 to about 10 hr. and a hydrogen to hydrocarbon moleratio of about 1:1 to about 20:1.

6. The process of claim 5 further characterized in that said reformingcatalyst comprises, on an elemental basis, about 0.01 to about 2.0 wt.percent platinum, and about 0.1 to about 2.0 wt. percent chlorine withan aluminum carrier material.

7. The process of claim 5 further characterized in that said refractoryinorganic oxide comprises a crystalline aluminosilicate.

8. The process of claim 1 further characterized in that said low-octane,high-boiling fraction consists of about 30 to about volume percent ofsaid alkylate product.

References Cited UNITED STATES PATENTS 2,401,649 6/ 1946 Lefl'er 208-702,684,325 7/1954 Deanesly 208-70 2,890,995 6/1959 Findlay 208 3,211,80310/1965 Chapman 20879 HERBERT LEVINE, Primary Examiner US. Cl. X.R.208-l7, 93, 141

